Process of treating metalliferous materials



UNITED STATES PATENT oFEroE.

HENRY B. HOVLAND, E miLu'rn, AND GEORGE B. FRANKFORTER, 0E MINNEAPOLIS,

MINNESOTA; SAID FRANKFORTER ASSIGNOR T0 SAID HOVLAND.

, Ito Drawing.

til

. l PROCESS OF TREATING METALLIFEROUS MATERIALS.

of'the invention, such as will enable others skilled in art to which it appertains to make and use the same.

This invention relates to processes of,

treating metalliferous materials; and it comprises treating metalliferous materials with a solvent for the metal sought in order to bring said metal into solution, precipitating the metal as a sulfid, and obtaining the precipitated sulfidi by a suitable flotation process. The invention is more fully set forth in the following description and claims.

In recent years much attention has beengiven to the treatment of ores, particularly low grade ores, by so-called' flotation processes, which, broadly speaking, consists in separating the desired constituent from associated gangue by causing it to float on the surface, where it is collected as a con centrate. Experience shows that the general class of metallic sulfids respond more readily toflotation methods than the general class of oxidized metals, including the oxids, carbonates, silicates, etc. l

As a matter of fact, flotation processes haveproved incapable of efiectively separating metallic oxids, carbonates, and other oxidized forms of metals, as well as particles of free metal from the accompanying nonmetalliferous gangue, such metalliferous matter sinking for the most part with the gangue. and being lost in the sands and slimes.

We are aware that it has been proposed to modify the character of non-sulfid ores by producing on the metallifel'ous particles thereof a'coating or superficial layer of metallic sulfid and then to concentrate by flotation in the usual ways. According to such methods it is recommended to treat the ore Specification of Letters Patent. Patented Liar, 30, 1920, Application filed August 15, 1913.. Serial No. 784,945.

with a sulfidizing agent under conditions such that the conversion. of the oxidized metal into sulfid takes place directly in situ or at the surface of each metalliferous particle; the metal itself, in efiect, not going into solution at any stage of the process so i far as is discernible.

An object of the present invention is to obviate the objections to such processes heretofore proposed for concentrating non-sulfid ores by flotation, and to so' treat metalliferous materials generally which are non- I sulfid or partially non-sulfid in character, as to enable a ready and substantially complete separation of the values therein from the gangue by flotation. Besides ores properly so-called, concentrates, slime's, tailings, etc, are also adapted for treatment according to the present invention.

A further object of the invention is to render feasible the concentration by flotation methods of values reasons that no method has heretofore been worked out, or even suggested so far as we know. for concentrating values in fluedust and slags by the herein described process of solution, precipitation and flotation.

Further objects of the invention will appear as the description proceeds.

In carrying out the present process, we treat an ore or other metalliferous material with a suitable solvent to bring into solution substantially all the particular metal or metals to be subsequently won by flotation, or so much thereof as is non-sulfid in character; and by means of a suitable sulfidizing agent we precipitate the dissolved metal as a suliid. Obtained in this way the precipltated metallic sulfid or mixture of precipi- I tated sulfids, present in-the material to be subjected to flotation, is all or very largely in astate of extreme subdivision approaching molecular fineness; and this means a con dition in which. the superficial area of the sulfid or sulfids exposed to'the action of surface tension or other forces operating to lift up the sulfid particles by flotation, is a maximum. Moreover, the subsequent flotation treatment yields a supernatant froth or scum of sulfids which is remarkably coherent and other metals may include, for example, silvet and gold. In particular we contemplate the treatment of materials containing the desired metal in some oxidized form such as an oxid, hydrate, carbonate, sulfate, silicate, etc, or a mixture of any two or more of these compounds.

We regard the treatment of copper bearing materials as the most important application of the present process, although the invention is not limited thereto. Thus copper ores such as copper oxids, chrysocolla, malachite, and azurite can be treated with entire success by our process and with careful work, the final yield of copper is substantially equal to thetheoretical copper content of the particular ore treated. Flue dust from copper smelting, containing gold and silver values in addition to copper,

, can also be treated for copper by the present process with particularly advantageous res'ults, since thesubstantially complete removal of copper leaves the'residue in ideal condition for extracting precious metal values therefrom by treatment with cyanid.

- Copper bearing slags can also be success-- fully treated by our process. J

These specific applications of the process we regard as of particular importance.

For purposes of illustration the application of the present process to a copper hearing material such as a chrysocolla andcop- )er carbonatefore may be briefly described. he ore is first suitably crushed and is best ground fairly fine, for example,-to 40 or mesh size, more or less, this being determined by. the character of the particular ore. A

quantit of rather dilute sulfuric acid solution, est containing in then'eighborhood of about 5 per cent. sulfuric acid, is then added and caused to react upon the ore, the quantity of acidused being advantageously somewhat in excess of that chemically equivalent to the copper in the ore being treated. Excess of acid prevents precipitation of acid soluble sulfids in the subse quent sulfidizing step. Solution of the copper may be expedited by suitable agitation and mixing. Free access of air during'the' dissolving operation is advantageous.

A sulfidizing agent such as hydrogen sulfid, either in gaseous form or in aqueous solution, is introduced into the pulpy freely flowing mixture, whereby the copper is precipitated as sulfid. During this step it is well to keep the mass in agitation in order to thoroughly. mix and aerate the reacting constituents. The metallic sulfid or sulfids thus obtained are artificially produced chemical precipitates and exhibit a marked tendency to coagulate, a property particularly advantageous in the subsequent steps.

As soon as precipitation of copper sulfid appears complete, a suitable quantity of oily matter, as kerosene, or of other equiva lent material is added to the pulp and agitation thereof under conditions favoring thorough aeration may be continued. lhe sulfids immediately begin to riseandcollect 0n the surface as a froth or scum which can be removed readily, while the gangue particles sink and are removed as tailings.

The details of the procedure just described can be varied considerably. After the precipitation of the copper as sulfid,

practically any effective flotation or separating method may be employed, that described being merely illustrative.

Instead of using as weak a solution of sulfuric acid as that indicated above, the

ore may be treated with stronger solutions at first, such as 10 per cent. or greater strength-followed by suitable dilution with water. Such procedure advantageously expedites solution with some ores.

Sulfuric acid is usually employed in this process as the ore solvent because 'of its general applicability and cheapness. Other solvents may under some conditions be employed.

. As above stated, a very important feature of the present invention is that it makes possible the successful treatment of flue dust, particularly flue dust from copper smelters. Heretofore the recovery of metallic values from flue dust has been a matter of expense and extreme difficulty.

The values carried by flue dust vary widely. A typical flue dust may contain from fl: to 15 per cent. co with considerable gold an silver. All the components of the furnace charge are also present in varying proportions. Almost invariably a flue dust is highly silicious.

Much of the copper is present in oxidized form and the compiuatively large copper per, more or less,

. vented the extraction of the precious metals a known 'methods. prepared by treating. copper matte with a silicious.

therefrom by cyaniding.

. By the present method it is possible to extract and separate the copper as well as the precious metals in flue dust with entire success. Generally speaking, the operation of treating flue dust may be conducted in much the same manner as described above for the treatmentv of a copper ore. Owing tothe exceptional complexity of th'ecombinations in which copper is present in flue dust, special conditions are sometimes required to dissolve the copper completely.

. For example, it is sometimes desirable to use a stronger acid solution than with ores, say as high as 20 per cent. sulfuric acid; and in some cases a small quantity of nitric acid may be added to the sulfuric acid solution. Heat may also be applied to expedite solution, the heat being readily obtained from the hot furnace gases in the vicinity. The residue of the flue dust, after removal of the copper, may. then be cyanided to recover precious metals.

Various sudfidizi'ng agents may be employed in our process, as, for example, hydrogen sulfid as a "gas or in solution, or a soluble sulfid such as an alkali sulfid. As a rule we find hydrogen sulfld the most convenient sulfidizing agent to use.

Where hydrogen sulfid is employed, it may be prepared according to any of the Or it is advantageously suitable acid, such as sulfuric acid. As a rule it is advisable to crush the matte to a suitable degree of fineness in order that the acid may have more ready access to the ferrous sulfid in the matter. Hydrogen sulfid may also be supplied in situ in the pulp by adding to and mixing with the pulp finely ground matte or other material liberatmg hydrogen sulfid in conjunctlon with an acid.

lit is to be understood that, while the process herein described is primarily adapted to the treatment of materials containing metal values in oxidized condition, nevertheless the presence of more or less metal sulfids inthe materials to be treated is not precluded. It frequently happens that a sulfid ore contains part of its metal values in oxidized condition, and such an ore is well adapted'to treatment in accordance with our invention, especially where the ore 1s hlghly It is to be understood I solvent as hereinbeforeemployed may include a single acid, or mixtures of acidsor alkalis orother'solvents. In general we may.

that the broad term closure that reagents may be regenerated in the process and that theremay'be unused surplus of reagents in the water passing out with the tailings, and, furthermore,

that such reagents may be recovered and used on fresh ores orimaterials.

' What we clalm 1s:

1 The processof obtaining metal values.

from material containing the same which comprises subjecting such material to the action of a solvent for the metal to be extracted from said material, precipitating the dissolved metal as sulfid in presence of gangue, and separating said sulfid from associated gangue by flotation.

2. The process of extracting copper values from copper bearing. material which comprises dissolving copper'from' such material by meansof a suitable solvent, precipisolved copper as sulfid in presence of gangue,

and separating the copper sulfid from .as-

sociated gangue by flotation.

4:. The process of extracting copper from materlal containing the same which comprises dissolving substantially all the copper present by means of a solution of sulfuric acid, precipitating copper as sulfid in presence of gangue, and separating copper sulfid from associated gangue by flotation.

5. The process of treating oxidized ores which comprises first dissolving certain metalliferous constituents with a suitable solvent, subsequently precipitatingsuch dis solved constituents back into the pulp as sulfids, and concentrating the resulting pulp by a flotation process.

-6. The process of treating oxidized ores which comprises dissolving certain metallif-' erous constituents with a suitable solvent, precipitating such dissolved constituents back intothe pulp as sulfid, and concentrating the resulting pulp by a flotation process.

7 The process of treating copper-contain ing oxidized ores which comprises dissolving the copper with a suitable solvent, precipitating the copper back into the pulp and concentrating the resulting pulp by a settling treatment. i

8. The process of treating copper-containing oxidized ores which comprises dis solving the copper with a suitable solvent,

precipitating the copper back into the pulp as sulfid and concentrating the resulting pulp by a flotation treatment.

9. The process of treating copper-containing oxidized ores which comprises dissolving the copper with dilute sulfuric acid, pretation process.

cipitating the copper back into the pulp as sulfid, and concentrating the pulp by a flo- 10. The process of obtaining metal values from material containing base" metal and precious metal which comprises subjecting such material to the. action of a solvent, precipitating dissolved metal as sulfid, back into the mass, concentrating the resulting material by flotation and recovercious metal, which comprises dis solving copper with a suitable solventg precipitating the copper, as sulfid, back into the mass, concentrating the resulting material by flotation and recovering precious metal from the residue by treatment with a precious metal solvent.

In testimony whereof we hereunto aflix our signatures in the preseiice of two witnesses.

HENRY B. HOVLAND.

GEORGE B. FRANKFORTER. Witnesses:

R. F. 'STEWARD,

E. O. HILDEBRAND. 

